Sunday, July 29, 2007

The Uncertainty of Warming Estimates

The Nature Reports: Climate Change website recently alerted readers to an oddity in the report of the United Nations Intergovernmental Panel on Climate Change. The IPCC is the source of the "consensus" on global warming/climate change that is often reported in the media.

At issue is something fundamental to any future planning we might do to deal with climate change. To make a long story short, Nature Reports, in the article "Quantifying Climate Change: Too Rosy a Picture?", suggest that the "consensus" conclusion doesn't take into account how uncertain science is about the factors that might warm or cool the planet.

The IPCC published this graph in 2001, showing how human activity is responsible for both warming and cooling effects on climate:

To start, notice that the chart is divided into pink and blue parts. The pink area is for warming effects, and the blue area is for cooling effects. On the left hand side we find carbon dioxide (CO2) and methane (CH4), which are often blamed for global warming. Human activity also produces ozone, which is a cooling effect in the stratosphere (upper atmosphere), but causes warming in the troposphere (the lower atmosphere).

So ozone, carbon dioxide, and methane, plus a few other pollutants, are responsible for some warming of the planet, according to this graph published by the IPCC. There is a little bit of cooling from stratospheric ozone, but not enough to offset the warming from low-altitude ozone, CO2, methane, and other gases. Next time, we'll look at cooling effects, and also begin to note some of the uncertainty of the science. Even the "consensus" report of the IPCC admits the science is uncertain.

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